Art of stabilizing soap



Pat nted May 12,1936 7 v 2,040,430

UNITED STATES PATENT :oFFlcE m or sTAnmzl'NG, soar Ernest O. Crocker, Belmont, and Lloyd F.'Henderson, Reading, Mass, assignors to Arthur D. Iittle,-lncorporated, Cambridge, Ma'ss., a corporation of Massachusetts v No Drawing. Application December 11, 1928,

' Serial No. 325,381 a 1 Claims. (01.87-16) This invention relates to a process of stabilizing practice. It is to be understood that the fore-,

soapin respect both to color and odor. The tendgoing proportions are merely illustrative oi nor-' 3? o soap, especially White soap; to take on mal and typical conditions, and of the nature of. w th age a yellowish color, either uniformly the problem, and .are by no means intended to a 5 throughout or in yellowish or brownish spots or define-any lmiform or standard condition nor any, 5 streaks, to lose its perfume and otherwise change limitation to which the invention is confinedits odor, is well known, and it is the object of the The presence of the metals in larger quantities present invention toobviate these objectionable than suggested as typical v-is, of course, even more. results. Such discoloration and change of odor injurious, and even in very much smaller quantihave been generally attributed to oxidation of ties produces appreciable deleterious effects in some of the ingredients of soap by the oxygen of the soap- Iron y and 11511811? -D n in the air, but the cause and mechanism or the greater q a y than pp but W have hr oxidation and the nature of the resulting deleserved that quantity for quantity copper is a vast.- terious eflects have been bscure; 131' more important factor than iron in promoting We have discoveredthat this oxidationis proxidation. Both. h wever, wh n pre nt, re 15 moted principally by the catalytic action or cera a t th pr s nt nv nt ontain multivalentmetals. ,Soap always contains We e discovered that pp and ttraces of multivalent meta1s,' especially copper ions promote oxidation of certain-ingredientso! and iron, which are harmful, and often zinc, t e oa T p s o i implies t em nickel, lead and tin, which are relatively non-inence of water or equivalent ionizing material. iurlous. Such metals come from various sources; Soap always contains w t The Oxidation s They may be picked up from th apparatus u characterized by the development of rancidi'ty, in making the soap, or from the vats and con- Whih u s accompanied by d hB tainers for the ingredients from which t 5094 the soap and by an unpleasant odor. Alteration is made. They ar present t some extent in t and weakening of the perfume is also a result of 25 original ingredients as a customary or as a natsuch oxidation. It is the aim of the present inural impurity; for example,'caustic soda and ventlon therefore to] remove the cause of the obtam vegetable ofls contain coppen Many Soap iectionable oxidation by substantially eliminattats are derived from waste sources and are more 8 j copper and-311131110115 (cations) and hence.

or less badly contaminated with metals; n nulllfying the oxidation-promoting action of the 30 a y perfume materials contain copper and metals. It is obviously not practicable physically sometimes other metals. But from whatever to'remove from the -P the copper and 1I011 sources t t may come. a soap Stock which are present in such exceedingly minute practically never free from traces of multivalent quamltlesi but We have Succeeded removink 1 metalm I g I the oxidation-promoting cationiorm of these The principal deleterious metals are the mulmetals h meanstivalent metals, copper and iron; the others are r T we have accomplished in twoswaysi first;

apparently negligible fromjthe point of view of by precipitating the mppel and iron; Second, by

40 dlscolomtiun and loss change of o c Iormingcomplexes of the copper and iron whereper and iron are normally present in the soap in the properties characteristic .of the metal catonly in minute -quant1ties while the ions are absent. Both methods'may bevtermed ,gmoun val-y widely in m e soap stocks demetalization or de-ionization; by which we mean Of catorder o fjone of copper to from one ions, is, the decrease of the" concentration t any nu parts of Soap and one part of of metal cations to the point where they are inimh t several hundred thousand parts of soap capable of appreciable oxidation promoting ac- But even in minute quantities of this order they 1 produce discoloration and change of odor. Quan- I carrying out the Precipitation method,

titles of copper too small to be detectable by orvwhich is u p e er ed ethod; we add to the-5 dinary analytical procedures can cause marked 1 leagent which T011115 With the pp a d failure of color and odor. For example, when o in the Dre-16110601 -D, ufic ently insoltwo partsoi copper per million parts of soap are uble precipitate so that the amount of metals intentionally added, the effects are soon detected, remaining in solution as cations is negligible,

and are far more severe than is usually found in thus eliminating the activating or promoting This material, while it may be considered, properly, as insoluble", is vastly more soluble than are the sulfides of iron and copper and hence is able to precipitate traces of iron and copper from soap, as the sulfides, particularly when it is present in excess of the amount needed for such precipitation,

By way of specific example of the application of the invention to the milling process of making soap the following procedure is recommended. Neat soap as it comes from the kettle in hot,

viscous-liquid form containing approximately- 70% soap and water, is chilled on rolls, from which it comes inthe form of moist shavings or sheets; the moist shavings arethen placed in a drier and" dried; from the drier the dried shavings are passed into'a mixer in which they are worked into a dough-like consistency by a kind I of churning action. The perfume materials are usually introduced into the mixer, and it is preferably at this stage also that we introduce the precipitating agent. Zinc sulfide, the preferred precipitating agent, i nthe form of a white powder and in the proportion of about .4% of the soap by weight, is put intov the mixer and there thoroughly mixed with and dispersed throughout a the soap mass. The quantity of precipitant thus.

recommended is in excess of that theoretically necessary toprecipitate the small amounts of soluble copper and iron normally present, but such excess is desirable as it furnishes a reserve of precipitating material against any emergency, such as the presence of more copper or iron than was expected, or later contamination by further processing, from wrappers, etc., or the efiects of atmospheric oxidation on the sulfide precipitates formed, in case the iron precipitate, for example, should slowly oxidize to sulfate by the action of atmospheric oxygen. In any of these events the excess of zinc sulfide, or other pre cipitating agent'used, will react'with the solubilized metal and again precipitate it.

After the soap leaves the mixer it is passed through the several mills, the plodder, the cutter and the press according to usual practice.

Other reagents beside zinc sulfide which, when added to copper and iron in alkaline solution, will form precipitates and act as eliminators of the copper and iron ions, are sodium'and other water soluble sulfides, such sulfur derivatives as can'form sulfides in the presence of copper and iron in soap, and other precipitants for traces of iron and copper in the presence of soap. Examples are lithopone, cryptone, methylene blue and thiourea.:

In general, any material which forms compounds of copper and iron which are less soluble in soap than are copper and iron soaps will act more or less well as a precipitant for this purpose. Methylene blue and thiourea are instances of organic compounds, which in time decompose, giving ofi' hydrogen sulfide, which is the actual precipitant.

As already mentioned, instead of adding the precipitating agent to the soap in the mixer, it

may be added to the neat soap as made in the kettle. While'this is an alternative (and less desirable) procedure in the manufacture of soap by the milling process, it is the only practicable procedure in the manufacture of soap by the ordinary frame process since in the frame process all steps from the chilling rolls to the plodder, both inclusive, are omitted and replaced by solidifying the neat soap in the frame and dividing it into bars preparatory for the cutting of it into cakes. Therefore the only feasible stage of the frame process for introducing the precipitating agent is into the fiuid or semifiuid neat soap before it goes to the frame.

The other method of demetalization, or decreasing the-concentration of metal ions sufficiently to nullify their oxidation-promoting action, isby forming complexes which either do not ionize at all, or if they ionize, do so with the metal in the complex ion, which is preferably the anion. Suitable reagents for such complex formation are: sodium salicylate and the organic salicylates; eugenol and a number of other phenols; water-soluble cyanides, and arsenites; alkali saltsof lactic, citric and tartaric acids; dimethyl glyoxime; thiourea; most sugars, but not sucrose; and sodium sulfosalicylate.

Any of these reagents when introduced into the soap, either in the mixer if the milling process is used, or into the neat soap from the kettle whether in the milling "process or the frame process, will result in the conversion of the traces of copper and iron ions in the soap into complexes wherein the metals are inactive and the oxidation-promoting properties characteristic of the simple metal cations are absent.

Sodium salicylate' has'been found to combine with copper and iron compounds, at the alkalinity of soap, to'make metal complexes which exist as highly colored solutions. These give none of the ordinary ionic reactions of the metals such as rapid precipitation by ferrocyanides or even by sulfides. The amounts of metals ordinarily present in the' soap, however, are not enough to color the cakes of soap appreciably.

The elimination of the ions ofcopper and iron as above described, whether by precipitation to remove the metal ions from solution in insoluble form, or by complex formation when a soluble, un-ionized metal compound without the ordinary metal cations is formed, eliminates the cause of the catalytic oxidation-promoting action and consequently the oxidation'of the ingredients of the soap and thereby prevents the development of "rancidity' with 'its resulting discoloration, change of odor and loss of perfume.

The process of dernetalization herein described, which'operates by eliminating the cause of oxidation by eliminating the ions of certain multivalent metals responsible for the catalytic promotion of oxldation, is to be sharply distinguished from the use of the so-called anti-oxidants, which have been proposed, at least experimentally, to lessen the ordinary oxidation which occurs in soap without removing its cause. I

Our process of stabilizing, protecting and preserving soap may easily andeconomically be applied to existing methods of making fine toilet soaps, and is applicable as well to the manufacture of common laundry and washing soaps;

It is our purpose, herein to claim the invention generically, and also to claim that species characterized by precipitation. The alternative species characterized by complex formation is not 2,040,480 herein claimed except as it exemplifies genus.

\ ing the milling operation.

4. The artof stabilizingsoap. containing ionized copper and "irohj-whichmomprises adding an excess of sulfide tothe'soap mass.

5. The art of stabilizing soap containing ionized copper and iron, which comprises adding an ex- 5 cess oi zinc sulfide to the soap mass.

6. The art cgif-s bilizinzisoap containing ionized copper, which conipding to; the soap mass an excessoi sulfide:

'1. The art of stabilizingsoap containing ionized 10 copper, which comprises adding an excess of zinc sulfide to the soap mass.

C. CRDCKER.

LLOYD F. HENDERSON. 

